(1) Field of the Invention
The present invention relates to a photocurable resin composition which is excellent in the photo-curability at low temperatures close to normal temperature and provides a cured product excellent in the adhesion characteristics such as the water-resistant adhesion strength and also in the hardness, strength and color tone. More particularly, the present invention relates to a photocurable resin composition which shows excellent properties as a curable composition for teeth, such as a tooth adhesive, a tooth composite resin or a tooth rigid resin.
(2) Description of the Prior Art
Various curable compositions comprising a radical-polymerizable monomer such as a (meth)acrylic acid ester type vinyl monomer and a polymerization initiator have been proposed as curable compositions for teeth, such as tooth adhesives, composite resins and rigid resins.
A tooth adhesive is required to have a high curing speed at low temperatures close to normal temperature and to provide a cured product excellent in the adhesion strength to teeth and the water-resistant adhesion strength. A tooth composite resin or tooth rigid resin is required to have a curability at low temperatures close to normal temperature and to provide a cured product which is excellent not only in the above-mentioned adhesion characteristics but also in the mechanical properties such as strength, compression strength, hardness and abrasion resistance and the color tone. With recent rapid progress of the tooth-repairing curative technique, the above-mentioned properties required for curable compositions for teeth become severe.
In connection with conventional curable compositions for teeth comprising a radical-polymerizable monomer such as a (meth)acrylic acid ester type vinyl monomer and a polymerization initiator, there have been proposed several methods in which a photopolymerization initiator is used as the polymerization initiator and photocuring is effected, whereby the above-mentioned properties are improved. For example, Japanese Patent Publications No. 10986/79 and No. 33687/78 propose a process in which polymerization is carried out in the presence of a photopolymerization initiator comprising a carbonyl compound such as .alpha.-diketone and an amine.
Even if this known combination of a carbonyl compound and an amine is used for photocuring a radical-polymerizable monomer of the (meth)acrylic acid ester type having an aromatic polycarboxylic acid or its anhydride structure and the cured product is applied to the above-mentioned uses of the photocurable resin composition for teeth, no satisfactory results can be obtained because the cured product is inferior in the color tone and water-resistant adhesion strength.
Recently, Japanese Patent Application Laid-Open Specification No. 5407/82 and DE-OS 3,029,276 teach that when a 2-cyanoethylamine, especially N-methyl-N-cyanoethylamine, is used as the amine promoter for the photopolymerizable composition, the curing-promoting action is enhanced and there can be attained effects of preventing coloration of the cured resin and eliminating the amine smell.
We previously found that when a composition comprising a radical-polymerizable monomer including 4-methacryloyloxyethoxycarbonylphthalic acid or its anhydride and a vinyl compound and a free radical generator is used as a tooth adhesive, a cured product excellent in the adhesion characteristics such as the adhesion strength and water-resistant adhesion strength is obtained, and we proposed this photocurable composition in Japanese Patent Application Laid-Open Specification No. 12338/79 and Japanese Patent Publication No. 17513/83.
This photocurable composition for teeth is excellent in the adhesion characteristics, mechanical properties and color tone but is still insufficient in the curing speed.